A small band of helicopter pilots risked their lives to rescue wounded soldiers during World War II.

Louis Carle thought his helicopter was small enough to land in a clearing on a jungle hilltop in Luzon. It was June 1945, the waning days of the Pacific war, and Carle, a second lieutenant in the U.S. Army Air Forces, was trying to evacuate a wounded American soldier from the main island in the Philippines. Carle began a cautious descent in his Sikorsky R-4B, but a rotor tip hit a tree, and with an abrupt jerk, the helicopter began thrashing itself to pieces.

After the helicopter hit the ground, Carle was helped from the wreckage. He found himself sitting in the midst of a small band of U.S. soldiers. Nearby, starving but well-armed Japanese squads were determined to resist to the end. With injuries to his head and leg and a splinter of a wood rotor blade lodged behind his right eye, Carle had no choice but to order the U.S. soldiers to fire bazooka rounds into the wreckage and destroy his helicopter. He then began an arduous trek out of the mountainous jungle. Before he reached safety, he encountered one of the Japanese soldiers. Carle, armed with a pistol, shot and killed him.

From June 15 to July 29, 1945, Carle and five other pilots evacuated 75 to 80 wounded soldiers, one or two at a time, from the highlands northeast of Manila. Although they were not the first helicopter pilots to fly in combat—that distinction belongs to Lieutenant Carter Harman of the First Air Commando Group, who flew the first medical evacuations, in Burma on April 23, 1944—they were the first to be targeted by enemy fire: Japanese soldiers tried to shoot them down with machine guns. Their six-week effort constitutes the largest combat helicopter operation before the Korean War, yet their contributions remain largely unknown.

The evacuation of casualties had been contemplated as a mission that helicopters could perform for the armed services, but it is not the mission that the six pilots were trained for, and it is not why their first-generation helicopters were sent to the Philippines. Pilots and helicopters had been assigned to the Pacific theater to ferry aircraft parts for a program known as Project Ivory Soap. With this project, the Army Air Forces used U.S. Army-owned ships as floating depots to maintain the aircraft of groups stationed in the Pacific. Early in the war, air groups often waited months for replacement parts and supplies to reach the Pacific isles on which they were based; with repair ships floating nearby, aircraft could be turned around much faster.

By December 1943, Project Ivory Soap had evolved into a fleet of six Liberty ships, designated Aircraft Repair Units (Floating), and 18 smaller ships, designated Aircraft Maintenance Units (Floating). In the final year of the war, the program proved essential for maintaining the tempo of Pacific-based aircraft operations by conducting nearly all of the most intensive maintenance functions, with the exception of engine overhaul.

By far the most distinctive feature of the floating repair ships was their helicopters. In addition to the R-4B, Sikorsky had made two other helicopters for World War II: the R-5 and R-6. The R-4 was a trainer intended merely to introduce the helicopter’s potential to the military; the R-6 was a further evolution, designed as a liaison aircraft. The R-5 was the true workhorse, the only one of the group capable of lifting a substantial load.

Unfortunately, the much larger R-5 suffered a series of engineering delays and was not ready for deployment until several months after the war ended. The R-6 also suffered delays, but saw limited service in the last three months of the war. That left the lowly R-4 trainer to bear the brunt of helicopter operations from April 1944 onward. Under ideal conditions, the R-4 could carry, in addition to the pilot and fuel, only 195 pounds, which meant only instruments and small components such as propeller hubs. But the timely delivery of even small payloads was highly valued.

The First Aircraft Repair Unit deployed on October 11, 1944, and by the following February, all six vessels were in the Pacific. At the start of June 1945, the Third, Fifth, and Sixth Aircraft Repair Units were operating in the Philippines, supporting the Fifth Air Force, while the remaining three supported the 20th Air Force in the Marianas. (The First and Second Aircraft Repair Units were specially equipped and trained to support B-29s in the Marianas, including repair of their radar and complex central fire control systems.) Each of the ships had a 40- by 72-foot steel deck for helicopter operations.

Carle and First Lieutenant Robert Cowgill were assigned to the Fifth Aircraft Repair Unit. On June 15, with Cowgill away to pick up the first Sikorsky R-6A to make it into the theater, the Fifth Air Force received a request from the 38th Infantry Division to evacuate two soldiers with head injuries from a spot 35 miles east of Manila.

Carle was immediately dispatched in one of the unit’s R-4s. Reaching what he thought was the designated spot, Carle recalled: “All hell broke loose as a hail of 100-pound bombs started dropping all around me. I got out of there but quick. When I got my breath back, I saw a squadron of P-47s dive-bombing the spot I had just been flying.” (Carle gave accounts of his rescue missions to Fred Duncan, the historian of the aircraft repair units, and me. We interviewed Carle and the other Ivory Soap pilots in 2000 and 2001 as part of an oral history project for the National Air and Space Museum. Carle died in 2000.)